RESULTS: By 1 year, the overall mean (SE) weight loss was 13.7 (1.8) kg, with no significant difference between groups (P = .26). Over the course of the study, there were significant time x diet interactions for Spielberger State Anxiety Inventory, Beck Depression Inventory, and Profile of Mood States scores for total mood disturbance, anger-hostility, confusion-bewilderment, and depression-dejection (P < .05) as a result of greater improvements in these psychological mood states for the LF diet compared with the LC diet. Working memory improved by 1 year (P < .001 for time), but speed of processing remained largely unchanged, with no effect of diet composition on either cognitive domain.

CONCLUSIONS: Over 1 year, there was a favorable effect of an energy-restricted LF diet compared with an isocaloric LC diet on mood state and affect in overweight and obese individuals. Both diets had similar effects on working memory and speed of processing. Trial Registration anzctr.org.au Identifier: 12606000203550.